TheWinter Olympics may showcase the best this world has to offer when it comes towinter sports, but how would such Olympians fare off this world? The idea ofice-skating on Mars or snowboarding on Europa might seem a little farfetched,but astronauts have actually skied on the moon.

Moonskiing

Theskiing that astronauts have tried on the moon was not on snow, but on moondust.

"Ithink downhill techniques would work very well on the moon," Schmittadded. "You even have built-in moguls, the impact craters on the slopes.Lunar gravity would allow all kinds of jumps and hops that you might finddifficult on Earth."

However,unlike true snow, moondustis very abrasive, far more so than sand. While typical grains of sand onEarth have rounded edges, moondust grains have very sharp edges "andscratch anything that comes in contact with them," Schmitt said, made asthey are from rocks shattered by millennia of meteor bombardment. Any skiing orsledding on the moon would require very tough equipment.

Martiansports

Winter Olympians on Earth only contend with normal ice, frost andsnow, but on Mars there are two kinds ? frozen water, and frozen carbondioxide, commonly known as "dry ice."

"In the winter at the poles, when it's dark all the time, itis snowingcarbon dioxide as it freezes out of the atmosphere, and that sticks to adepth of 1 to 3 meters (3 to 10 ft.) and then melts away ? actually, sublimesaway, goes from solid to gas ? when the sun comes up again during polarspring," said Mike Caplinger, a senior scientist at Malin Space ScienceSystems in San Diego. "The residual north polar cap ? the part that's leftin the summer ? is exposed water ice."

Any snow on the surface of Mars made of water "is more likefrost than snow," Caplinger noted. In a similar way, the carbon dioxidesnow on Mars "is more like ice than snow, so I'd question if skiing isreally possible. Maybe the scenes of skating along the Martian canals inHeinlein's book 'Red Planet' were a little prescient."

However, skating on Mars would face challenges. Under idealconditions, skaters glide on the ice because of a thin layer of water theirskates create by friction and pressure. However, given the cold andextraordinarily thin air of the red planet, even if the water ice and dry icegot warm enough, instead of melting, both would sublime instead.

"You wouldn't get as much purchase with skates," saidresearch astrophysicist Scott Sandford at NASA Ames Research Center in MoffettField, Calif. Planetary geophysicist Steve Vance at the Jet PropulsionLaboratory in Pasadena, Calif., noted that one might instead want roller skateson Martian ice, "although one would have to be careful to choose wheelsthat wouldn't become brittle at those cold temperatures."

And just as snowstorms on Earth can shut down skiing, "you dohave big dust stormsoccasionally on Mars, sometimes even global ones," Sandford noted.

DangerousEuropa

TheJovian moon of Europa might at first seem a great place for ice-skating sinceits surface is covered in ice and seems extraordinarily flat.

However, "its surface isn't shiny and reflective, which meansit's not smooth, clear ice, the kind you'd want to skate on," Vance said."Most likely, there's what you'd think of as snow on the surface, theproduct of the breakdown of ice from radiation and from impacts."

The surfaceof Europa and other icy moons "are probably not so great forice-skating but they might be good for cross-country and other skiingevents," Vance noted. Moreover, "many have naturally occurringsnowboard half-pipes that stretch for hundreds of miles." On Europa, theseare most likely caused by gravitational tides that are constantly squeezingEuropa and changing the shape of its surface.

Given the extraordinarily tenuous atmosphere on Europa ? with anatmospheric pressure a trillionth or so that of Earth's ? "you don't haveto worry about things like aerodynamic drag, so there's no need to crouch ifyou're going downhill, and it may be easier to steer with a differentposture," Sandford said.

Still, Caplinger noted "the radiation environment on Europais so harsh that I wouldn't want to be doing anything there, certainly notskating!" Jupiter has the largest and most powerful of all the planetarymagnetospheres in the solar system, resulting in dangerous belts of radiation.

Although radiation is less of an issue on Mars, Sandford notedthat one danger there is how its thin atmosphere would provide virtually noprotection against any bursts of energy from the sun.

Wintereverywhere

Atsome level, even if sportsin space don't involve ice or snow or frost, "they're still wintersports in the sense that you have to equip yourself against extreme cold,"Sandford said.

Sandford noted one main difference when it comes to sports inspace is the weaker gravity athletes would often find. On the moon, gravity isabout one-sixth Earth's; on Mars; a little more than one-third; on Europa, alittle less than one-seventh.

"That means your muscles feel stronger ? you're able to jumpfarther, but when it comes to skiing, you'd accelerate more slowly going downthe hill," Sandford said. "You'd also have to adjust how you maketurns, since you're not pushing off with the same strength as on Earth. Also,it might be more difficult to change direction, since you're not held to theground as greatly. You might want to compensate by getting more contact withthe ground ? maybe bigger skis would help you turn better. Of course, therewould then be competing effects ? skis would be heavier, and it'd be harder forankles to turn."

Ski jumping would be quite different under lower gravity ?"you might need much longer ramps since there would be lessacceleration," Sandford said. "Also, without the presence of any air,you'd have the competing effects of having no air resistance, making for longerjump, but also no ability to lean forward to generate aerodynamic lift, makingfor shorter jumps. In any event, you really don't want to fall and do a faceplant and maybe crack your helmet. You wouldn't just get a zero ? you'd bedead."

To deal with any radiation, especially on Europa, "one mightconsider lead suits," Sandford said. The additional mass of such a suitmight also "provide a muscle workout more similar to what you would getfor comparable exercise on Earth," Vance added.

Thespacesuits that athletes would have to wear means that a great deal of theirmass would be outside their bodies, and that fact coupled with the low gravity"means that astronauts had problems moving," Vance noted."Normal walking didn't work so well on the moon, so they did skippingmotions instead, and there would likely be similar issues when it came tosports."

Snowballfights: Only on Earth

Surprisingly,snowball fights are virtually impossible anyplace else in the solar system butEarth. The reason that snowballs hold together is because snow melts slightlywhen squeezed here. The combination of extreme cold and weak atmospheres foundelsewhere in the solar system where ice exists means that any attempts to molda snowball might only work if you brought along a heated hydraulic press,Sandford explained. "Of course, you could alwayshack out a lump of ice from the surface around you and throw that, but I thinkit's universally understood by kids everywhere that this is extremely badform."

Instead,any would-be athletes in space might come up with new sports one could never dohere.

"Thereare probably lots of opportunities," Sandford said. "One can imaginethat if one ever got to Pluto, or the Neptunian satellite Triton, there are a lotof nitrogen ices out there, which sublime fairly rapidly at 30 Kelvin (-405degrees F). One could imagine wearing heated shoes to generate an explosivepuff of gas whenever one's foot touched the ground for launch jumping."

Although sports in space might simply be flights of fancy,"certainly if we go out to these bodies, we have to give thought topractical issues of traveling from one place to another, and might have to givethought to how machines or people would perform to work on snow or ice,"Sandford said.

"In any case, people are people ? if they hang out longenough, they'll probably compete with each other after a while," Sandfordsaid. "When the astronauts went up in Apollo, lo and behold, they broughtgolf clubs. Even if you go for totally scientific reasons, people will bemonkeying around. While a classic snowball fight might be impossible, I'm surethey'd think of something to do."